1. Field of the Invention
The present invention relates to an infrared transmission/reception apparatus and an infrared transmission/reception method, particularly to an infrared transmission/reception apparatus which uses a data link protocol IrLAP (IrDA Link Access Protocol) standardized by industrial corporation IrDA (Infrared Data Association) and performs infrared communication and a transmission/reception method utilizing the apparatus.
2. Description of the Prior Art
Infrared communication has heretofore been known in which infrared light is used to perform communication among apparatuses. According to the infrared communication, for a distance of about 1 m from a communication object the communication can be performed without performing connection via a cable, and the like, which is convenient for use, and which provides an advantage that the communication can be realized with a simple constitution as compared with the communication using radio waves. From such advantage, the infrared communication is preferably applied to small apparatuses such as a note type personal computer and a portable information terminal.
Additionally, the small apparatus provided with the infrared communication function is in many cases operated by a battery incorporated inside so that it is convenient when a user carries it during movement, and it is preferable that power consumption be minimized also to lengthen the continuous operation possible time of the small apparatus. Therefore, it is preferable to suppress even the intensity of the infrared light radiated during data transmission in the infrared communication to the minimum, and to reduce the power consumption.
In the apparatus provided with a conventional infrared communication function, however, the infrared light with a constant intensity is constantly radiated regardless of the communication distance. Therefore, when the communication distance is short, the infrared light with an excessive intensity is radiated, and power is consumed more than necessary. Conversely, when the communication distance is long, no infrared light with a necessary intensity is radiated, and there is a possibility that communication cannot be performed.
As the conventional infrared transmission/reception apparatus for solving the problem, the apparatuses disclosed in Japanese Patent Application Laid-Open Nos. 83443/1997 and 299479/1998 are known.
The apparatus disclosed in the Japanese Patent Application Laid-Open No. 83443/1997 controls a driver to drive a light emitting LED based on the size of a noise component in a received signal, so that the current flowing through the light emitting LED and the infrared transmission intensity are controlled.
Moreover, the apparatus disclosed in the Japanese Patent Application Laid-Open No. 200479/1998 first radiates the infrared light with a maximum intensity, gradually lowers the intensity when an opposite apparatus can perform communication without any reception error, and performs the communication with an optimum radiation intensity without generating any reception error in the opposite apparatus.
Additionally, the infrared communication is standardized by IrDA standard, and the apparatuses conforming to the standard can mutually perform data communication by the infrared light. In the IrDA standard the protocol regarding the infrared communication is divided into a plurality of layers and defined, and in the IrLAP which is one of the plurality of layers the protocol is defined to establish a communication link between the apparatuses.
In the infrared transmission/reception apparatus which conforms to the IrDA standard, a calling side apparatus (hereinafter referred to as the xe2x80x9cprimary stationxe2x80x9d) transmits a station finding command, an apparatus which can receive this station finding command and perform communication (hereinafter referred to as the xe2x80x9csecondary stationxe2x80x9d) transmits a station finding response to indicate its presence, and subsequently the primary station and secondary station start the infrared communication.
In the conventional infrared transmission/reception apparatus which conforms to the IrDA standard, the infrared communication intensity is always set to be constant. For example, when the primary station transmits the station finding command with the constant intensity and no station finding response is returned, it is judged that there is no apparatus able to perform the infrared communication nearby and the infrared communication is discontinued.
Additionally, Japanese Patent Application Laid-Open No. 1630/1990 discloses a remote operation apparatus which is not the infrared transmission/reception apparatus for performing data transmission/reception, but which remotely operates an air conditioner, and the like by the infrared light. This remote operation apparatus is constituted to raise the infrared communication intensity when no response information can be received from the operation objects such as the air conditioner.
The above-described conventional apparatus has the following problems.
First, in the apparatus disclosed in Japanese Patent Application Laid-Open No. 83443/1997, only the size of the noise component of the received signal is used as a parameter, and it is not defined whether the received signal can be recognized as data or not. Therefore, with the infrared communication intensity determined based on the size of the noise component, a state in which data communication is sufficiently enabled without any communication error cannot possibly be obtained.
Specifically, in the apparatus disclosed in the Japanese Patent Application Laid-Open No. 83443/1997, it is very difficult to obtain the relation between the size of the noise component and the infrared communication intensity to be used, and the apparatus is disadvantageously impractical.
Moreover, for the apparatus disclosed in the Japanese Patent Application Laid-Open No. 200479/1998, the opposite apparatus requires a function of detecting a communication error and transmitting error information, and there is a problem that general-purpose properties are lacking. Since the infrared light is necessarily transmitted first with a maximum intensity during communication start, there is also a problem that the power consumption increases in some cases.
Furthermore, in the conventional infrared transmission/reception apparatus which conforms the IrDA standard, since the infrared communication intensity is always set to be constant, there is a problem that in some state the infrared light with the excessive intensity is radiated and the power consumption is consumed more than necessary.
Additionally, the apparatus disclosed in the Japanese Patent Application Laid-Open No. 1630/1990 is the remote operation apparatus for operating the air conditioner, and the like, is basically a one-directional communication apparatus which transmits instructions to the operation object apparatuses such as the air conditioner in one direction, and is fundamentally different from the infrared transmission/reception apparatus whose object is a bidirectional data communication.
The present invention has been made in view of the above-described problems, and an object thereof is to provide an infrared transmission/reception apparatus which can perform communication with a required minimum infrared output regardless of an opposite apparatus and an infrared transmission/reception method.
In order to attain the above-described object, according to the present invention, there is provided an infrared transmission/reception apparatus which can function alone without depending on a communication object and which can perform transmission output level control.
According to the present invention, to attain the above-described object, there is provided an infrared transmission/reception apparatus which uses the station finding command of a data link protocol xe2x80x9cIrLAPxe2x80x9d standardized by a standardization corporation IrDA, and which can function alone and perform the transmission output level control.
Specifically, according to the present invention, in a primary station of an infrared communication system of IrDA standard in which a secondary station transmits a station finding response to a station finding command from the primary station, an infrared transmission output is changed to transmit a plurality of station finding commands, the infrared transmission output is used when the plurality of station finding commands to which the station finding response is returned from the secondary station are transmitted, and the subsequent communication is performed. According to this constitution, in the primary station of the infrared communication system, a minimum infrared transmission output can be selected in a communicable range, and the infrared transmission output can be reduced.
Moreover, according to the present invention, in a secondary station of an infrared communication system of IrDA standard in which the secondary station transmits a station finding response to a station finding command from a primary station, the station finding response is transmitted via a predetermined infrared transmission output during reception of the station finding command, a processing of successively raising the infrared transmission output and transmitting the station finding response with respect to the resent station finding command is repeated when no response is returned from the primary station with respect to the station finding response, the infrared transmission output is used when the response is returned from the primary station with respect to the station finding response, and the subsequent communication is performed. According to this constitution, in the secondary station of the infrared communication system, the minimum infrared transmission output can be selected in the communicable range, and the infrared transmission output can be reduced.
In other words, according to the present invention, since the electric current value can automatically be set to the value with which the infrared communication can normally be performed by increasing/decreasing the current flowing through the light emitting element in a stepwise manner, regardless of the communication distance, the power consumed in the light emitting element for transmitting the infrared data can be minimized regardless of the communication distance in a range in which the infrared communication can constantly and normally be performed.
Further, in the present invention, since the station finding command and station finding response defined by the heretofore standardized IrDA standard are used to perform the control for adjusting the transmission output, the type of the opposite apparatus is not limited, no large-scaled change is made from the conventional infrared communication system, and superior practicability is provided.
Still further, in the present invention, since the primary station receives the station finding response, and employs the output level for securely performing the communication, the securement of the output level adjustment is effectively high.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative examples.